Rheology modified pretreatment compositions and associated methods of use

ABSTRACT

Disclosed are methods for treating metal substrates that include contacting the metal with pretreatment compositions comprising: (a) a group IIIB metal, a group IVB metal and/or a group VB metal; and (b) a rheology modifier composition.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with Government support under Contract No.W912HQ-09-C-0038 awarded by SERDP. The United States Government may havecertain rights in this invention.

FIELD OF THE INVENTION

The present invention relates to pretreatment compositions, methods fortreating a metal substrate, including aluminum containing substrates andferrous substrates, such as cold rolled steel and electrogalvanizedsteel. The present invention also relates to coated metal substrates.

BACKGROUND INFORMATION

The use of protective coatings on metal substrates for improvedcorrosion resistance and paint adhesion is common. Conventionaltechniques for coating such substrates include techniques that involvepretreating the metal substrate with a pretreatment composition and/orwith an electrodepositable coating composition.

During processing or simply upon exposure to the atmosphere afterpretreating, a metal oxide layer, i.e., rust, is often formed over allor part of pretreated metal surface, thereby impairing its appearanceand/or suitability for further use.

It would, therefore, be desirable to provide methods for preventing orminimizing rust on a pretreated substrate, including those that areoriented in a substantially vertical fashion.

SUMMARY OF THE INVENTION

In certain respects, the present invention is directed to pretreatmentcompositions for treating a metal substrate comprising: (a) a group IIIBmetal, a group IVB metal and/or a group VB metal; and (b) a rheologymodifier composition.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances.

As previously mentioned, certain embodiments of the present inventionare directed to methods for treating a metal substrate. Suitable metalsubstrates for use in the present invention include those that are oftenused in the assembly of automotive bodies, automotive parts, and otherarticles, such as small metal parts, including fasteners, i.e., nuts,bolts, screws, pins, nails, clips, buttons, and the like. Specificexamples of suitable metal substrates include, but are not limited to,cold rolled steel, hot rolled steel, steel coated with zinc metal, zinccompounds, or zinc alloys, such as electrogalvanized steel, hot-dippedgalvanized steel, galvanealed steel, and steel plated with zinc alloy.Also, aluminum alloys, aluminum plated steel and aluminum alloy platedsteel substrates may be used. Other suitable non-ferrous metals includecopper and magnesium, as well as alloys of these materials. Moreover,the bare metal substrate being coating by the methods of the presentinvention may be a cut edge of a substrate that is otherwise treatedand/or coated over the rest of its surface. The metal substrate coatedin accordance with the methods of the present invention may be in theform of, for example, a sheet of metal or a fabricated part.

The substrate to be treated in accordance with the methods of thepresent invention may first be cleaned to remove grease, dirt, or otherextraneous matter. This is often done by employing mild or strongalkaline cleaners, such as are commercially available and conventionallyused in metal pretreatment processes. Examples of alkaline cleanerssuitable for use in the present invention include Chemkleen 163,Chemkleen 177, and Chemkleen 490MX, each of which is commerciallyavailable from PPG Industries, Inc. Such cleaners are often followedand/or preceded by a water rinse.

As previously indicated, certain embodiments of the present inventionare directed to methods treating a metal substrate that comprisecontacting the metal substrate with a pretreatment compositioncomprising a group IIIB metal, a group IVB metal and/or a group VB metaland a rheology modifier. As used herein, the term “pretreatmentcomposition” refers to a composition that upon contact with thesubstrate, reacts with and chemically alters the substrate surface andbinds to it to form a protective layer.

Often, the pretreatment composition comprises a carrier, often anaqueous medium, so that the composition is in the form of a solution ordispersion of a group IIIB metal, a group IVB metal and/or a group VBmetal in the carrier. In these embodiments, the solution or dispersionmay be brought into contact with the substrate by any of a variety ofknown techniques, such as dipping or immersion, spraying, intermittentspraying, dipping followed by spraying, spraying followed by dipping,brushing, or roll-coating. In certain embodiments, the solution ordispersion when applied to the metal substrate is at a temperatureranging from 60 to 150° F. (15 to 65° C.). The contact time is oftenfrom 10 seconds to 30 minutes, such as 30 seconds to 10 minutes.

As noted above, in certain embodiments, the pretreatment compositionalso comprises a rheology modifier. As used herein, the term “rheologymodifier” refers to a material that, when added to the pretreatmentcomposition, produces a thickened composition with a highly shearthinning, thixotropic rheology. As a result, the pretreatmentcomposition is sprayable using typical spray devices (including thosementioned below) and yet, it has been discovered, remains on thesurface, even if the surface is oriented substantially vertically. Asused herein, the term “substantially vertically” means substantiallyperpendicular (i.e., within ±20% from perpendicular) to the ground orother surface upon which the ferrous metal-containing surface isdisposed.

In certain of these embodiments, the rheology modifier comprises acolloidal layered silicate, often referred to as synthetic hectoriteclay. Colloidal layered silicates that are suitable for use in thecompositions described herein include, for example, LAPONITE RD,LAPONITE RDS, LAPONITE XL21 and LAPONITE JS, including combinationsthereof. LAPONITE RD is a free flowing synthetic layered silicate havinga bulk density of 1,000 kg/m³, a surface area (BET) of 370 m²/g, a pH ofa 2% suspension in water of 9.8, wherein the composition on a dry basisby weight is 59.5% SiO₂, 27.5% MgO, 0.8% Li₂O, and 2.8% Na₂O. LAPONITERDS is also a free flowing a free flowing synthetic layered silicatehaving a bulk density of 1,000 kg/m³, a surface area (BET) of 330 m²/g,a pH of a 2% suspension in water of 9.7, wherein the composition on adry basis by weight is 54.5% SiO₂, 26.0% MgO, 0.8% Li₂O, 5.6% Na₂O, and4.1% P₂O₅. LAPONITE XL21 is sodium magnesium fluorosilicate. Theparticle size of the colloidal layered silicates, such as thosedescribed above, is typically 1 to 30 nanometers in average diameter.

In certain embodiments, the colloidal layered silicate is present in thecomposition used in the methods of the present invention in an amount ofat least 1 percent by weight, such as at least 2 percent by weight, or,in some cases, at least 3 percent by weight, with the weight percentsbeing based on the total weight of the composition. In certainembodiments, the colloidal layered silicate is present in thecomposition used in the methods of the present invention in an amount ofno more than 10 percent by weight, such as no more than 6 percent byweight, or, in some cases, no more than 5 percent by weight, with theweight percents being based on the total weight of the composition.

Indeed, it was a surprising discovery that the use of rheology modifiersas defined herein such as synthetic hectorite clay, as opposed to otherthickening agents, including other thixotropic clays (such as kaolin andbentonite clays), produces a pretreatment composition that is bothsprayable at ambient conditions and remains in contact with thesubstrate surface even when the surface is oriented substantiallyvertically. By maintaining the pretreatment composition, andspecifically the group IIIB, IVB and/or group VB metal, in constantcontact with the substrate surface, surface drying and flash rusting onthe substrate surface are substantially reduced or prevented. As usedherein, “ambient conditions” refers to 23° C. and atmospheric pressure.

As used herein, the term “group IIIB, IVB and/or group VB metal” refersto an element that is in group IIIB or group IVB of the CAS PeriodicTable of the Elements as is shown, for example, in the Handbook ofChemistry and Physics, 63^(rd) edition (1983). Where applicable, themetal themselves may be used. In certain embodiments, a group IIIB, IVBand/or group VB metal compound is used. As used herein, the term “groupIIIB, IVB and/or group VB metal compound” refers to compounds thatinclude at least one element that is in group IIIB or group IVB or groupVB of the CAS Periodic Table of the Elements.

In certain embodiments, the group IIIB, IVB and/or group VB metalcompound used in the pretreatment composition is a compound ofzirconium, titanium, hafnium, yttrium, cerium, vanadium, or a mixturethereof. Suitable compounds of zirconium include, but are not limitedto, hexafluorozirconic acid, alkali metal and ammonium salts thereof,ammonium zirconium carbonate, zirconyl nitrate, zirconium carboxylatesand zirconium hydroxy carboxylates, such as hydrofluorozirconic acid,zirconium acetate, zirconium oxalate, ammonium zirconium glycolate,ammonium zirconium lactate, ammonium zirconium citrate, and mixturesthereof. Suitable compounds of titanium include, but are not limited to,fluorotitanic acid and its salts. A suitable compound of hafniumincludes, but is not limited to, hafnium nitrate. A suitable compound ofyttrium includes, but is not limited to, yttrium nitrate. A suitablecompound of cerium includes, but is not limited to, cerous nitrate.

In certain embodiments, the group IIIB, IVB and/or group VB metalcompound is present in the pretreatment composition in an amount of atleast 10 ppm metal, such as at least 100 ppm metal, or, in some cases,at least 150 ppm metal. In certain embodiments, the group IIIB, IVBand/or group VB metal compound is present in the pretreatmentcomposition in an amount of no more than 5000 ppm metal, such as no morethan 1000 ppm metal, or, in some cases, no more than 500 ppm metal. Theamount of group IIIB, IVB and/or group VB metal in the pretreatmentcomposition can range between any combinations of the recited valuesinclusive of the recited values.

In certain embodiments, the pretreatment composition also comprises anelectropositive metal that is not a group IIIB, IVB and/or group VBmetal. As used herein, the term “electropositive metal” refers to metalsthat are more electropositive than the metal substrate. This means that,for purposes of the present invention, the term “electropositive metal”encompasses metals that are less easily oxidized than the metal of themetal substrate. As will be appreciated by those skilled in the art, thetendency of a metal to be oxidized is called the oxidation potential, isexpressed in volts, and is measured relative to a standard hydrogenelectrode, which is arbitrarily assigned an oxidation potential of zero.The oxidation potential for several elements is set forth in the tablebelow. An element is less easily oxidized than another element if it hasa voltage value, E*, in the following table, that is greater than theelement to which it is being compared.

Element Half-cell reaction Voltage, E* Potassium K⁺ + e → K −2.93Calcium Ca²⁺ + 2e → Ca −2.87 Sodium Na⁺ + e → Na −2.71 Magnesium Mg²⁺ +2e → Mg −2.37 Aluminum Al³⁺ + 3e → Al −1.66 Zinc Zn²⁺ + 2e → Zn −0.76Iron Fe²⁺ + 2e → Fe −0.44 Nickel Ni²⁺ + 2e → Ni −0.25 Tin Sn²⁺ + 2e → Sn−0.14 Lead Pb²⁺ + 2e → Pb −0.13 Hydrogen 2H⁺ + 2e → H₂ −0.00 CopperCu²⁺ + 2e → Cu  0.34 Mercury Hg₂ ²⁺ + 2e → 2Hg  0.79 Silver Ag⁺ e → Ag 0.80 Gold Au³⁺ + 3e → Au  1.50

Thus, as will be apparent, when the metal substrate comprises one of thematerials listed earlier, such as cold rolled steel, hot rolled steel,steel coated with zinc metal, zinc compounds, or zinc alloys, hot-dippedgalvanized steel, galvanealed steel, steel plated with zinc alloy,aluminum alloys, aluminum plated steel, aluminum alloy plated steel,magnesium and magnesium alloys, suitable electropositive metals fordeposition thereon in accordance with the present invention include, forexample, nickel, copper, silver, and gold, as well mixtures thereof.

In certain embodiments, the source of electropositive metal in thepretreatment composition is a water soluble metal salt. In certainembodiments of the present invention, the water soluble metal salt is awater soluble copper compound. Specific examples of water soluble coppercompounds, which are suitable for use in the present invention include,but are not limited to, copper cyanide, copper potassium cyanide, coppersulfate, copper nitrate, copper pyrophosphate, copper thiocyanate,disodium copper ethylenediaminetetraacetate tetrahydrate, copperbromide, copper oxide, copper hydroxide, copper chloride, copperfluoride, copper gluconate, copper citrate, copper lauroyl sarcosinate,copper formate, copper acetate, copper propionate, copper butyrate,copper lactate, copper oxalate, copper phytate, copper tartarate, coppermalate, copper succinate, copper malonate, copper maleate, copperbenzoate, copper salicylate, copper aspartate, copper glutamate, copperfumarate, copper glycerophosphate, sodium copper chlorophyllin, copperfluorosilicate, copper fluoroborate and copper iodate, as well as coppersalts of carboxylic acids in the homologous series formic acid todecanoic acid, copper salts of polybasic acids in the series oxalic acidto suberic acid, and copper salts of hydroxycarboxylic acids, includingglycolic, lactic, tartaric, malic and citric acids.

When copper ions supplied from such a water-soluble copper compound areprecipitated as an impurity in the form of copper sulfate, copper oxide,etc., it may be preferable to add a complexing agent that suppresses theprecipitation of copper ions, thus stabilizing them as a copper complexin the solution.

In certain embodiments, the copper compound is added as a copper complexsalt such as K₃Cu(CN)₄ or Cu-EDTA, which can be present stably in thecomposition on its own, but it is also possible to form a copper complexthat can be present stably in the composition by combining a complexingagent with a compound that is difficulty soluble on its own. Examplesthereof include a copper cyanide complex formed by a combination of CuCNand KCN or a combination of CuSCN and KSCN or KCN, and a Cu-EDTA complexformed by a combination of CuSO₄ and EDTA.2Na.

With regard to the complexing agent, a compound that can form a complexwith copper ions can be used; examples thereof include inorganiccompounds, such as cyanide compounds and thiocyanate compounds, andpolycarboxylic acids, and specific examples thereof includeethylenediaminetetraacetic acid, salts of ethylenediaminetetraaceticacid, such as dihydrogen disodium ethylenediaminetetraacetate dihydrate,aminocarboxylic acids, such as nitrilotriacetic acid and iminodiaceticacid, oxycarboxylic acids, such as citric acid and tartaric acid,succinic acid, oxalic acid, ethylenediaminetetramethylenephosphonicacid, and glycine.

In certain embodiments, the electropositive metal, such as copper, isincluded in the pretreatment compositions in an amount of at least 1ppm, such as at least 5 ppm, or in some cases, at least 10 ppm of totalmetal (measured as elemental metal). In certain embodiments, theelectropositive metal is included in such pretreatment compositions inan amount of no more than 500 ppm, such as no more than 100 ppm, or insome cases, no more than 50 ppm of total metal (measured as elementalmetal). The amount of electropositive metal in the pretreatmentcomposition can range between any combinations of the recited valuesinclusive of the recited values.

In some embodiments, the pretreatment composition may be a silane or anon-crystalline phosphate, such as iron phosphate, containingpretreatment composition. Suitable silane containing pretreatmentcompositions include, but are not limited to, certain commerciallyavailable products, such as Silquest A-1100 Silane, which iscommercially available from Momentive Performance Materials. Suitablenon-crystalline phosphate containing pretreatment composition includepretreatment composition that comprise, iron phosphate, manganesephosphate, calcium phosphate, magnesium phosphate, cobalt phosphate, oran organophosphate and/or organophosphonate, such as is disclosed inU.S. Pat. No. 5,294,265 at col. 1, line 53 to col. 3, line 12 and U.S.Pat. No. 5,306,526 at col. 1, line 46 to col. 3, line 8, the citedportions of which being incorporated herein by reference. Suitablenon-crystalline phosphate containing pretreatment compositions arecommercially available, such as Chemfos® 158 and Chemfos® 51, which areiron phosphate pretreatment compositions commercially available from PPGIndustries, Inc.

In certain embodiments, the pretreatment composition comprises aresinous binder. Suitable resins include reaction products of one ormore alkanolamines and an epoxy-functional material containing at leasttwo epoxy groups, such as those disclosed in U.S. Pat. No. 5,653,823. Insome cases, such resins contain beta hydroxy ester, imide, or sulfidefunctionality, incorporated by using dimethylolpropionic acid,phthalimide, or mercaptoglycerine as an additional reactant in thepreparation of the resin. Alternatively, the reaction product is that ofthe diglycidyl ether of Bisphenol A (commercially available from ShellChemical Company as EPON 880), dimethylol propionic acid, anddiethanolamine in a 0.6 to 5.0:0.05 to 5.5:1 mole ratio. Other suitableresinous binders include water soluble and water dispersible polyacrylicacids as disclosed in U.S. Pat. Nos. 3,912,548 and 5,328,525; phenolformaldehyde resins as described in U.S. Pat. Nos. 5,662,746; watersoluble polyamides such as those disclosed in WO 95/33869; copolymers ofmaleic or acrylic acid with allyl ether as described in Canadian patentapplication 2,087,352; and water soluble and dispersible resinsincluding epoxy resins, aminoplasts, phenol-formaldehyde resins,tannins, and polyvinyl phenols as discussed in U.S. Pat. No. 5,449,415.

In these embodiments of the present invention, the resinous binder ispresent in the pretreatment composition in an amount of 0.005 percent to30 percent by weight, such as 0.5 to 3 percent by weight, based on thetotal weight of the ingredients in the composition.

In other embodiments, however, the pretreatment composition issubstantially free or, in some cases, completely free of any resinousbinder. As used herein, the term “substantially free”, when used withreference to the absence of resinous binder in the pretreatmentcomposition, means that any resinous binder is present in thepretreatment composition in an amount of less than 0.005 percent byweight. As used herein, the term “completely free” means that there isno resinous binder in the pretreatment composition at all.

In certain embodiments, the pH of the pretreatment composition may beadjusted to a pH between 2 and 8, such as between 4 and 6, such as to apH of 5, with one or more acids. Suitable acids that may be utilizedinclude organic acids and/or mineral acids.

In certain embodiment, the organic acid comprises a carboxylic acid. Incertain embodiments, the carboxylic acid has a water solubility of >1g/L at 20° C. Carboxylic acids suitable for use include, for example,monocarboxylic acids, such as formic acid, acetic acid, propionic acid,methylacetic acid, butyric acid, ethylacetic acid, n-valeric acid,n-butanecarboxylic acid, acrylic acid, propiolic acid, methacrylic acid,palmitic acid, stearic acid, oleic acid, linolic acid, and linolenicacid; dicarboxylic acids, such as oxalic acid, malonic acid, succinicacid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaicacid, lepargilic acid, sebacic acid, maleic acid, and fumaric acid;aliphatic hydroxy acids, such as glycolic acid, lactic acid, tartronicacid, glyceric acid, malic acid, tartaric acid, citramalic acid, citricacid, isocitric acid, leucine acid, mevalonic acid, pantoic acid,recinoleic acid, ricinelaidic acid, cerebronic acid, quinic acid, andshikimic acid; aromatic hydroxy acids, such as salicylic acid, creosoteacid, vanillic acid, syringic acid, pyrocatechuic acid, resorcylic acid,protocatechuic acid, gentisic acid, orsellinic acid, gallic acid,mandelic acid, benzilic acid, atrolactinic acid, melilotic acid,phloretic acid, coumaric acid, umbellic acid, caffeic acid, ferulicacid, and sinapic acid. Mixtures of any of the foregoing may also beused.

Mineral acids suitable for use to adjust the pH include, for example,phosphoric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid,and nitric acid. Mixtures of any of the foregoing may also be used.

In certain of these embodiments, the acid is added prior to the additionof the group IIIB, group IVB and/or group VB metal.

In certain embodiments, the pretreatment solution is formed by firstadding the rheology modifier composition, such as the colloidal layeredsilicate, to an aqueous medium while stirring. The pH of the resultantsolution is then adjusted to between 2 and 8 using one or more acidsfrom the group of acids described above. The group IIIB, group IVBand/or group VB metal (or metal compound) is then added to the pHadjusted solution, followed by the electropositive metal and/or anyother optional materials, such as complexing agents, silanes ornon-crystalline phosphate, or a resinous binder (described above orbelow).

The pretreatment composition may optionally contain other materials,such as nonionic surfactants and auxiliaries conventionally used in theart of pretreatment. In an aqueous medium, water dispersible organicsolvents, for example, alcohols with up to about 8 carbon atoms, such asmethanol, isopropanol, and the like, may be present; or glycol etherssuch as the monoalkyl ethers of ethylene glycol, diethylene glycol, orpropylene glycol, and the like. When present, water dispersible organicsolvents are typically used in amounts up to about ten percent byvolume, based on the total volume of aqueous medium.

Other optional materials include surfactants that function as defoamersor substrate wetting agents, such as those materials and amountsdescribed earlier with respect to the plating solution.

In certain embodiments, the pretreatment composition also comprises areaction accelerator, such as nitrite ions, nitro-group containingcompounds, hydroxylamine sulfate, persulfate ions, sulfite ions,hyposulfite ions, peroxides, iron (III) ions, citric acid ironcompounds, bromate ions, perchlorinate ions, chlorate ions, chloriteions as well as ascorbic acid, citric acid, tartaric acid, malonic acid,succinic acid and salts thereof. Specific examples of suitable materialsand their amounts are described in United States Patent ApplicationPublication No. 2004/0163736 A1 at [0032] to [0041], the cited portionof which being incorporated herein by reference.

In certain embodiments, the pretreatment composition also comprises afiller, such as a siliceous filler. Non-limiting examples of suitablefillers include silica, mica, montmorillonite, kaolinite, asbestos,talc, diatomaceous earth, vermiculite, natural and synthetic zeolites,cement, calcium silicate, aluminum silicate, sodium aluminum silicate,aluminum polysilicate, alumina silica gels, and glass particles. Inaddition to the siliceous fillers other finely divided particulatesubstantially water-insoluble fillers may also be employed. Examples ofsuch optional fillers include carbon black, charcoal, graphite, titaniumoxide, iron oxide, copper oxide, zinc oxide, antimony oxide, zirconia,magnesia, alumina, molybdenum disulfide, zinc sulfide, barium sulfate,strontium sulfate, calcium carbonate, and magnesium carbonate.

As indicated, in certain embodiments, the pretreatment composition issubstantially or, in some cases, completely free of chromate and/orheavy metal phosphate. As used herein, the term “substantially free”when used in reference to the absence of chromate and/or heavy metalphosphate, such as zinc phosphate, in the pretreatment composition meansthat these substances are not present in the composition to such anextent that they cause a burden on the environment. That is, they arenot substantially used and the formation of sludge, such as zincphosphate, formed in the case of using a treating agent based on zincphosphate, is eliminated.

Moreover, in certain embodiments, the pretreatment composition issubstantially free, or, in some cases, completely free of any organicmaterials. As used herein, the term “substantially free”, when used withreference to the absence of organic materials in the composition, meansthat any organic materials are present in the composition, if at all, asan incidental impurity. In other words, the presence of any organicmaterial does not affect the properties of the composition. As usedherein, the term “completely free” means that there is no organicmaterial in the composition at all.

In certain embodiments, the film coverage of the residue of thepretreatment coating composition generally ranges from 1 to 1000milligrams per square meter (mg/m²), such as 10 to 400 mg/m². Thethickness of the pretreatment coating can vary, but it is generally verythin, often having a thickness of less than 1 micrometer, in some casesit is from 1 to 500 nanometers, and, in yet other cases, it is 10 to 300nanometers.

In certain embodiments of the methods of the present invention, afterthe substrate is contacted with the pretreatment composition, it is thencontacted with a coating composition comprising a film-forming resin.

As used herein, the term “film-forming resin” refers to resins that canform a self-supporting continuous film on at least a horizontal surfaceof a substrate upon removal of any diluents or carriers present in thecomposition or upon curing at ambient or elevated temperature.Conventional film-forming resins that may be used include, withoutlimitation, those typically used in automotive OEM coating compositions,automotive refinish coating compositions, industrial coatingcompositions, architectural coating compositions, coil coatingcompositions, and aerospace coating compositions, among others.

In certain embodiments, the coating composition comprises athermosetting film-forming resin. As used herein, the term“thermosetting” refers to resins that “set” irreversibly upon curing orcrosslinking, wherein the polymer chains of the polymeric components arejoined together by covalent bonds. This property is usually associatedwith a cross-linking reaction of the composition constituents ofteninduced, for example, by heat or radiation. Curing or crosslinkingreactions also may be carried out under ambient conditions. Once curedor crosslinked, a thermosetting resin will not melt upon the applicationof heat and is insoluble in solvents. In other embodiments, the coatingcomposition comprises a thermoplastic film-forming resin. As usedherein, the term “thermoplastic” refers to resins that comprisepolymeric components that are not joined by covalent bonds and therebycan undergo liquid flow upon heating and are soluble in solvents.

In certain embodiments, the coating composition is part of a multi-layercoating composition applied to the pretreated substrate. The coatinglayers could include an electrocoating layer formed from anelectrodepositable coating composition (such as those described below),suitable top coat layers (e.g., base coat, clear coat layer, pigmentedmonocoat, and color-plus-clear composite compositions). It is understoodthat suitable topcoat layers include any of those known in the art, andeach independently may be waterborne, solventborne, in solid particulateform (i.e., a powder coating composition), or in the form of a powderslurry. The top coat typically includes the film-forming resin asdescribed above, crosslinking material and, if a colored base coat ormonocoat is utilized, one or more pigments. In certain embodiments, oneor more of the topcoat layers are applied onto a substantially uncuredunderlying layer. For example, in some embodiments, a clear coat layeris applied onto at least a portion of a substantially uncured basecoatlayer (wet-on-wet), and both layers are simultaneously cured in adownstream process. Suitable other coating layers thus can includeautomotive coatings, automotive refinish coatings, and/or CARC (chemicalagent resistant coatings) coating compositions.

As previously indicated, in certain embodiments, the substrate iscontacted with a coating composition comprising a film-forming resin byan electrocoating step wherein an electrodepositable composition isdeposited onto the metal substrate by electrodeposition. In the processof electrodeposition, the metal substrate being treated, serving as anelectrode, and an electrically conductive counter electrode are placedin contact with an ionic, electrodepositable composition. Upon passageof an electric current between the electrode and counter electrode whilethey are in contact with the electrodepositable composition, an adherentfilm of the electrodepositable composition will deposit in asubstantially continuous manner on the metal substrate.

Electrodeposition is usually carried out at a constant voltage in therange of from 1 volt to several thousand volts, typically between 50 and500 volts. Current density is usually between 1.0 ampere and 15 amperesper square foot (10.8 to 161.5 amperes per square meter) and tends todecrease quickly during the electrodeposition process, indicatingformation of a continuous self-insulating film.

The electrodepositable composition utilized in certain embodiments ofthe present invention often comprises a resinous phase dispersed in anaqueous medium wherein the resinous phase comprises: (a) an activehydrogen group-containing ionic electrodepositable resin, and (b) acuring agent having functional groups reactive with the active hydrogengroups of (a).

In certain embodiments, the electrodepositable compositions utilized incertain embodiments of the present invention contain, as a mainfilm-forming polymer, an active hydrogen-containing ionic, oftencationic, electrodepositable resin. A wide variety of electrodepositablefilm-forming resins are known and can be used in the present inventionso long as the polymers are “water dispersible,” i.e., adapted to besolubilized, dispersed or emulsified in water. The water dispersiblepolymer is ionic in nature, that is, the polymer will contain anionicfunctional groups to impart a negative charge or, as is often preferred,cationic functional groups to impart a positive charge.

Examples of film-forming resins suitable for use in anionicelectrodepositable compositions are base-solubilized, carboxylic acidcontaining polymers, such as the reaction product or adduct of a dryingoil or semi-drying fatty acid ester with a dicarboxylic acid oranhydride; and the reaction product of a fatty acid ester, unsaturatedacid or anhydride and any additional unsaturated modifying materialswhich are further reacted with polyol. Also suitable are the at leastpartially neutralized interpolymers of hydroxy-alkyl esters ofunsaturated carboxylic acids, unsaturated carboxylic acid and at leastone other ethylenically unsaturated monomer. Still another suitableelectrodepositable film-forming resin comprises an alkyd-aminoplastvehicle, i.e., a vehicle containing an alkyd resin and an amine-aldehyderesin. Yet another anionic electrodepositable resin compositioncomprises mixed esters of a resinous polyol, such as is described inU.S. Pat. No. 3,749,657 at col. 9, lines 1 to 75 and col. 10, lines 1 to13, the cited portion of which being incorporated herein by reference.Other acid functional polymers can also be used, such as phosphatizedpolyepoxide or phosphatized acrylic polymers as are known to thoseskilled in the art.

As aforementioned, it is often desirable that the activehydrogen-containing ionic electrodepositable resin (a) is cationic andcapable of deposition on a cathode. Examples of such cationicfilm-forming resins include amine salt group-containing resins, such asthe acid-solubilized reaction products of polyepoxides and primary orsecondary amines, such as those described in U.S. Pat. Nos. 3,663,389;3,984,299; 3,947,338; and 3,947,339. Often, these amine saltgroup-containing resins are used in combination with a blockedisocyanate curing agent. The isocyanate can be fully blocked, asdescribed in U.S. Pat. No. 3,984,299, or the isocyanate can be partiallyblocked and reacted with the resin backbone, such as is described inU.S. Pat. No. 3,947,338. Also, one-component compositions as describedin U.S. Pat. No. 4,134,866 and DE-OS No. 2,707,405 can be used as thefilm-forming resin. Besides the epoxy-amine reaction products,film-forming resins can also be selected from cationic acrylic resins,such as those described in U.S. Pat. Nos. 3,455,806 and 3,928,157.

Besides amine salt group-containing resins, quaternary ammonium saltgroup-containing resins can also be employed, such as those formed fromreacting an organic polyepoxide with a tertiary amine salt as describedin U.S. Pat. Nos. 3,962,165; 3,975,346; and 4,001,101. Examples of othercationic resins are ternary sulfonium salt group-containing resins andquaternary phosphonium salt-group containing resins, such as thosedescribed in U.S. Pat. Nos. 3,793,278 and 3,984,922, respectively. Also,film-forming resins which cure via transesterification, such asdescribed in European Application No. 12463 can be used. Further,cationic compositions prepared from Mannich bases, such as described inU.S. Pat. No. 4,134,932, can be used.

In certain embodiments, the resins present in the electrodepositablecomposition are positively charged resins which contain primary and/orsecondary amine groups, such as described in U.S. Pat. Nos. 3,663,389;3,947,339; and 4,116,900. In U.S. Pat. No. 3,947,339, a polyketiminederivative of a polyamine, such as diethylenetriamine ortriethylenetetraamine, is reacted with a polyepoxide. When the reactionproduct is neutralized with acid and dispersed in water, free primaryamine groups are generated. Also, equivalent products are formed whenpolyepoxide is reacted with excess polyamines, such asdiethylenetriamine and triethylenetetraamine, and the excess polyaminevacuum stripped from the reaction mixture, as described in U.S. Pat.Nos. 3,663,389 and 4,116,900.

In certain embodiments, the active hydrogen-containing ionicelectrodepositable resin is present in the electrodepositablecomposition in an amount of 1 to 60 percent by weight, such as 5 to 25percent by weight, based on total weight of the electrodeposition bath.

As indicated, the resinous phase of the electrodepositable compositionoften further comprises a curing agent adapted to react with the activehydrogen groups of the ionic electrodepositable resin. For example, bothblocked organic polyisocyanate and aminoplast curing agents are suitablefor use in the present invention, although blocked isocyanates are oftenpreferred for cathodic electrodeposition.

Aminoplast resins, which are often the preferred curing agent foranionic electrodeposition, are the condensation products of amines oramides with aldehydes. Examples of suitable amine or amides aremelamine, benzoguanamine, urea and similar compounds. Generally, thealdehyde employed is formaldehyde, although products can be made fromother aldehydes, such as acetaldehyde and furfural. The condensationproducts contain methylol groups or similar alkylol groups depending onthe particular aldehyde employed. Often, these methylol groups areetherified by reaction with an alcohol, such as a monohydric alcoholcontaining from 1 to 4 carbon atoms, such as methanol, ethanol,isopropanol, and n-butanol. Aminoplast resins are commercially availablefrom American Cyanamid Co. under the trademark CYMEL and from MonsantoChemical Co. under the trademark RESIMENE.

The aminoplast curing agents are often utilized in conjunction with theactive hydrogen containing anionic electrodepositable resin in amountsranging from 5 percent to 60 percent by weight, such as from 20 percentto 40 percent by weight, the percentages based on the total weight ofthe resin solids in the electrodepositable composition.

As indicated, blocked organic polyisocyanates are often used as thecuring agent in cathodic electrodeposition compositions. Thepolyisocyanates can be fully blocked as described in U.S. Pat. No.3,984,299 at col. 1, lines 1 to 68, col. 2, and col. 3, lines 1 to 15,or partially blocked and reacted with the polymer backbone as describedin U.S. Pat. No. 3,947,338 at col. 2, lines 65 to 68, col. 3, and col. 4lines 1 to 30, the cited portions of which being incorporated herein byreference. By “blocked” is meant that the isocyanate groups have beenreacted with a compound so that the resultant blocked isocyanate groupis stable to active hydrogens at ambient temperature but reactive withactive hydrogens in the film forming polymer at elevated temperaturesusually between 90° C. and 200° C.

Suitable polyisocyanates include aromatic and aliphatic polyisocyanates,including cycloaliphatic polyisocyanates and representative examplesinclude diphenylmethane-4,4′-diisocyanate (MDI), 2,4- or 2,6-toluenediisocyanate (TDI), including mixtures thereof, p-phenylenediisocyanate, tetramethylene and hexamethylene diisocyanates,dicyclohexylmethane-4,4′-diisocyanate, isophorone diisocyanate, mixturesof phenylmethane-4,4′-diisocyanate and polymethylenepolyphenylisocyanate. Higher polyisocyanates, such as triisocyanates canbe used. An example would includetriphenylmethane-4,4′,4″-triisocyanate. Isocyanate ( )-prepolymers withpolyols such as neopentyl glycol and trimethylolpropane and withpolymeric polyols such as polycaprolactone diols and triols (NCO/OHequivalent ratio greater than 1) can also be used.

The polyisocyanate curing agents are typically utilized in conjunctionwith the active hydrogen containing cationic electrodepositable resin inamounts ranging from 5 percent to 60 percent by weight, such as from 20percent to 50 percent by weight, the percentages based on the totalweight of the resin solids of the electrodepositable composition.

The electrodepositable compositions described herein are in the form ofan aqueous dispersion. The term “dispersion” is believed to be atwo-phase transparent, translucent or opaque resinous system in whichthe resin is in the dispersed phase and the water is in the continuousphase. The average particle size of the resinous phase is generally lessthan 1.0 and usually less than 0.5 microns, often less than 0.15 micron.

The concentration of the resinous phase in the aqueous medium is oftenat least 1 percent by weight, such as from 2 to 60 percent by weight,based on total weight of the aqueous dispersion. When such compositionsare in the form of resin concentrates, they generally have a resinsolids content of 20 to 60 percent by weight based on weight of theaqueous dispersion.

The electrodepositable compositions described herein are often suppliedas two components: (1) a clear resin feed, which includes generally theactive hydrogen-containing ionic electrodepositable resin, i.e., themain film-forming polymer, the curing agent, and any additionalwater-dispersible, non-pigmented components; and (2) a pigment paste,which generally includes one or more pigments, a water-dispersible grindresin which can be the same or different from the main-film formingpolymer, and, optionally, additives such as wetting or dispersing aids.Electrodeposition bath components (1) and (2) are dispersed in anaqueous medium which comprises water and, usually, coalescing solvents.

As aforementioned, besides water, the aqueous medium may contain acoalescing solvent. Useful coalescing solvents are often hydrocarbons,alcohols, esters, ethers and ketones. The preferred coalescing solventsare often alcohols, polyols and ketones. Specific coalescing solventsinclude isopropanol, butanol, 2-ethylhexanol, isophorone,2-methoxypentanone, ethylene and propylene glycol and the monoethylmonobutyl and monohexyl ethers of ethylene glycol. The amount ofcoalescing solvent is generally between 0.01 and 25 percent, such asfrom 0.05 to 5 percent by weight based on total weight of the aqueousmedium.

In addition, a colorant and, if desired, various additives such assurfactants, wetting agents or catalyst can be included in the coatingcomposition comprising a film-forming resin. As used herein, the term“colorant” means any substance that imparts color and/or other opacityand/or other visual effect to the composition. The colorant can be addedto the composition in any suitable form, such as discrete particles,dispersions, solutions and/or flakes. A single colorant or a mixture oftwo or more colorants can be used.

Example colorants include pigments, dyes and tints, such as those usedin the paint industry and/or listed in the Dry Color ManufacturersAssociation (DCMA), as well as special effect compositions. A colorantmay include, for example, a finely divided solid powder that isinsoluble but wettable under the conditions of use. A colorant can beorganic or inorganic and can be agglomerated or non-agglomerated.Colorants can be incorporated by use of a grind vehicle, such as anacrylic grind vehicle, the use of which will be familiar to one skilledin the art.

Example pigments and/or pigment compositions include, but are notlimited to, carbazole dioxazine crude pigment, azo, monoazo, disazo,naphthol AS, salt type (lakes), benzimidazolone, condensation, metalcomplex, isoindolinone, isoindoline and polycyclic phthalocyanine,quinacridone, perylene, perinone, diketopyrrolo pyrrole, thioindigo,anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone,anthanthrone, dioxazine, triarylcarbonium, quinophthalone pigments,diketo pyrrolo pyrrole red (“DPPBO red”), titanium dioxide, carbon blackand mixtures thereof. The terms “pigment” and “colored filler” can beused interchangeably.

Example dyes include, but are not limited to, those that are solventand/or aqueous based such as phthalo green or blue, iron oxide, bismuthvanadate, anthraquinone, perylene, aluminum and quinacridone.

Example tints include, but are not limited to, pigments dispersed inwater-based or water miscible carriers such as AQUA-CHEM 896commercially available from Degussa, Inc., CHARISMA COLORANTS andMAXITONER INDUSTRIAL COLORANTS commercially available from AccurateDispersions division of Eastman Chemical, Inc.

As noted above, the colorant can be in the form of a dispersionincluding, but not limited to, a nanoparticle dispersion. Nanoparticledispersions can include one or more highly dispersed nanoparticlecolorants and/or colorant particles that produce a desired visible colorand/or opacity and/or visual effect. Nanoparticle dispersions caninclude colorants such as pigments or dyes having a particle size ofless than 150 nm, such as less than 70 nm, or less than 30 nm.Nanoparticles can be produced by milling stock organic or inorganicpigments with grinding media having a particle size of less than 0.5 mm.Example nanoparticle dispersions and methods for making them areidentified in U.S. Pat. No. 6,875,800 B2, which is incorporated hereinby reference. Nanoparticle dispersions can also be produced bycrystallization, precipitation, gas phase condensation, and chemicalattrition (i.e., partial dissolution). In order to minimizere-agglomeration of nanoparticles within the coating, a dispersion ofresin-coated nanoparticles can be used. As used herein, a “dispersion ofresin-coated nanoparticles” refers to a continuous phase in which isdispersed discreet “composite microparticles” that comprise ananoparticle and a resin coating on the nanoparticle. Exampledispersions of resin-coated nanoparticles and methods for making themare identified in United States Patent Application Publication2005-0287348 A1, filed Jun. 24, 2004, U.S. Provisional Application No.60/482,167 filed Jun. 24, 2003, and U.S. patent application Ser. No.11/337,062, filed Jan. 20, 2006, which is also incorporated herein byreference.

Example special effect compositions that may be used include pigmentsand/or compositions that produce one or more appearance effects such asreflectance, pearlescence, metallic sheen, phosphorescence,fluorescence, photochromism, photosensitivity, thermochromism,goniochromism and/or color-change. Additional special effectcompositions can provide other perceptible properties, such as opacityor texture. In certain embodiments, special effect compositions canproduce a color shift, such that the color of the coating changes whenthe coating is viewed at different angles. Example color effectcompositions are identified in U.S. Pat. No. 6,894,086, incorporatedherein by reference. Additional color effect compositions can includetransparent coated mica and/or synthetic mica, coated silica, coatedalumina, a transparent liquid crystal pigment, a liquid crystal coating,and/or any composition wherein interference results from a refractiveindex differential within the material and not because of the refractiveindex differential between the surface of the material and the air.

In certain embodiments, a photosensitive composition and/or photochromiccomposition, which reversibly alters its color when exposed to one ormore light sources, can be used in the present invention. Photochromicand/or photosensitive compositions can be activated by exposure toradiation of a specified wavelength. When the composition becomesexcited, the molecular structure is changed and the altered structureexhibits a new color that is different from the original color of thecomposition. When the exposure to radiation is removed, the photochromicand/or photosensitive composition can return to a state of rest, inwhich the original color of the composition returns. In certainembodiments, the photochromic and/or photosensitive composition can becolorless in a non-excited state and exhibit a color in an excitedstate. Full color-change can appear within milliseconds to severalminutes, such as from 20 seconds to 60 seconds. Example photochromicand/or photosensitive compositions include photochromic dyes.

In certain embodiments, the photosensitive composition and/orphotochromic composition can be associated with and/or at leastpartially bound to, such as by covalent bonding, a polymer and/orpolymeric materials of a polymerizable component. In contrast to somecoatings in which the photosensitive composition may migrate out of thecoating and crystallize into the substrate, the photosensitivecomposition and/or photochromic composition associated with and/or atleast partially bound to a polymer and/or polymerizable component inaccordance with certain embodiments of the present invention, haveminimal migration out of the coating. Example photosensitivecompositions and/or photochromic compositions and methods for makingthem are identified in U.S. application Ser. No. 10/892,919 filed Jul.16, 2004, incorporated herein by reference.

In general, the colorant can be present in the coating composition inany amount sufficient to impart the desired visual and/or color effect.The colorant may comprise from 1 to 65 weight percent, such as from 3 to40 weight percent or 5 to 35 weight percent, with weight percent basedon the total weight of the compositions.

After deposition, the coating is often heated to cure the depositedcomposition. The heating or curing operation is often carried out at atemperature in the range of from 120 to 250° C., such as from 120 to190° C. for a period of time ranging from 10 to 60 minutes. In certainembodiments, the thickness of the resultant film is from 10 to 50microns.

Illustrating the invention are the following examples that are not to beconsidered as limiting the invention to their details. All parts andpercentages in the examples, as well as throughout the specification,are by weight unless otherwise indicated.

EXAMPLES

Coating compositions were prepared as follows:

Cleaner 1:

Chemkleen 166 HP/171ALF, alkaline cleaner [commercially available fromPPG Industries, Inc.]

Pretreatment 1:

CHEMFOS 700/CHEMSEAL 59, immersion applied tricationic Zn phosphate andsealer [commercially available from PPG Industries, Inc.]

Pretreatment 2:

Experimental rheology modified zirconium pretreatment with Copper wasprepared by dissolving 4% (w/w) Laponite RD in 500 g of H2O and adding70% nitric acid dropwise to a pH=5. Hexafluorozirconic acid was thenadded to give a zirconium concentration of 500 ppm. Copper (II) nitratewas also added to give a copper concentration of 20 ppm. Afterpretreatment in the zirconium pretreatment solution, the panels wererinsed thoroughly with deionized water and then dried with a warm airblowoff.

Pretreatment 3:

Experimental rheology modified zirconium pretreatment based on zirconylacetate was prepared by dissolving 4% (w/w) Laponite RD in 500 g of H2Oand adding 70% nitric acid dropwise to a pH=5. Zirconyl acetate was thenadded to give a zirconium concentration of 500 ppm. After pretreatmentin the zirconium pretreatment solution, the panels were rinsedthoroughly with deionized water and then dried with a warm air blowoff.

Pretreatment 4:

Experimental rheology modified zirconium pretreatment based on zirconylnitrate was prepared by dissolving 4% (w/w) Laponite RD in 500 g of H2Oand adding 70% nitric acid dropwise to a pH=4. Zirconyl nitrate was thenadded to give a zirconium concentration of 500 ppm. After pretreatmentin the zirconium pretreatment solution, the panels were rinsedthoroughly with deionized water and then dried with a warm air blowoff.

Pretreatment 5:

Experimental rheology modified zirconium pretreatment using Laponite OG(a lithium magnesium sodium silicate) was prepared by dissolving 2.75%(w/w) Laponite OG in 1556 g of H2O and adding 70% nitric acid dropwiseto a pH=5. Hexafluorozirconic acid was then added to give a zirconiumconcentration of 1000 ppm. Copper (II) nitrate was also added to give acopper concentration of 40 ppm. After pretreatment in the zirconiumpretreatment solution, the panels were rinsed thoroughly with deionizedwater and then dried with a warm air blowoff.

Pretreatment 6:

Experimental rheology modified zirconium pretreatment using LaponiteXL21 (a sodium magnesium fluorosilicate) was prepared by dissolving 3%(w/w) Laponite XL21 in 1552 g of H2O and adding 70% nitric acid dropwiseto a pH=5. Hexafluorozirconic acid was then added to give a zirconiumconcentration of 1000 ppm. Copper (II) nitrate was also added to give acopper concentration of 40 ppm. After pretreatment in the zirconiumpretreatment solution, the panels were rinsed thoroughly with deionizedwater and then dried with a warm air blowoff.

Pretreatment 7:

Experimental rheology modified zirconium pretreatment using LaponiteXL21 (a sodium magnesium fluorosilicate) was prepared by dissolving2.75% (w/w) Laponite XL21 in 97.25 g of H2O and adding 70% nitric aciddropwise to a pH=5. Hexafluorozirconic acid was then added to give azirconium concentration of 500 ppm. Copper (II) nitrate was also addedto give a copper concentration of 10 ppm.

Pretreatment 8:

Experimental rheology modified zirconium pretreatment using Kaolin(naturally occurring clay) was prepared by dissolving 2.75% (w/w) Kaolin(available from VWR International) in 97.25 g of H2O and adding 70%nitric acid dropwise to a pH=5. Hexafluorozirconic acid was then addedto give a zirconium concentration of 500 ppm. Copper (II) nitrate wasalso added to give a copper concentration of 10 ppm.

Pretreatment 9:

Experimental rheology modified zirconium pretreatment using Bentonite(naturally occurring clay) was prepared by dissolving 2.75% (w/w)Bentonite (available from VWR International) in 97.25 g of H2O andadding 70% nitric acid dropwise to a pH=5. Hexafluorozirconic acid wasthen added to give a zirconium concentration of 500 ppm. Copper (II)nitrate was also added to give a copper concentration of 10 ppm.

Paint 1:

Amine-catalyzed epoxy made in accordance with United States Militaryspecification Mil-P-53022.

Paint 2:

Enviro-prime® 7000P, a cathodic electrocoat commercially available fromPPG Industries.

Test 1:

20 cycles of GM-9511P.

Test 2:

40 cycles of GM-9511P.

Test 3:

500 hrs B117 neutral salt spray (ASTM Standard B117).

Test 4:

20 cycles of GMW14872.

Experimental Procedure:

The coating systems were cleaned using Cleaner 1, rinsed with deionizedwater, and pretreated using a plastic pipette to coat evenly with thepanels in a vertical orientation for 5 minutes at 27° C. Panels werethen rinsed with deionized water and dried by for 5 minutes at 55° C.using forced air.

The example coating (Paint 1) composition was applied at 0.0009-0.0011inch dry film thickness and allowed to cure at ambient conditions for 7days prior to testing.

The example coating (Paint 2) composition was applied at 0.0008-0.0010inches and cured for 25 minutes at 175° C. in an electric oven.

Example 1 Scope of Zirconium Compounds

Pretreatment 1 was evaluated against Pretreatment 2-4 for resistance toTest 1 and 2. Cold-rolled panels (ACT Panels) were cleaned using Cleaner1, rinsed with deionized water, and pretreated using a plastic pipetteto coat evenly with the panels in a vertical orientation for 5 minutesat 27° C. Panels were then rinsed with deionized water and dried by for5 minutes at 55° C. using forced air.

Pretreatments were evaluated by coating them with Paint 1 or Paint 2curing as suggested above, and then subjecting them to 20 cycle hoursGM-9511P (Test 1).

Samples were then scribed vertically and placed in Test 1 for 20 or 40cycles.

TABLE 1 Corrosion Performance Paint 1, 20 cycle Paint 2, GM9511P,GM9511P, mm mm Pretreatment 4.0  5.2 1 Pretreatment 4.6  7.0 2Pretreatment 4.8 11.0 3 Pretreatment 6.6  9.0 4

Example 2 Synthetic Clay Type

Pretreatment 1 was evaluated against Pretreatment 5 and 6 for resistanceto Test 3 and 4. Cold-rolled panels (ACT Panels) were cleaned usingCleaner 1, rinsed with deionized water, and pretreated using a plasticpipette to coat evenly with the panels in a vertical orientation for 5minutes at 27° C. A set of CRS (ACT) panels were cleaned using Cleaner1, but without any additional pretreatment were included. Panels werethen rinsed with deionized water and dried by for 5 minutes at 55° C.using forced air.

Pretreated and clean-only panels were evaluated by coating them withPaint 1 and curing as suggested above. Samples were then scribedvertically and placed in Test 3 for 500 hours and Test 4 for 20 cycles.

TABLE 2 Corrosion Performance 500 hours 20 cycle B117, GMW14872, mm mmPretreatment  2.6 4.4 1 Pretreatment 20.0 5.0 5 Pretreatment 11.0 4.8 6Cleaner 1 34.2 7.0

Example 3 Clay Type

The rheological effect of Laponite clay was compared to two otherconventional clays. The rheology profiles of Pretreatments 7-9 weremeasured using a Paar-Physica MCR 301 Rheometer. The table below liststhe viscosity as a function of shear rate. A high viscosity at low shearrate indicates that the Laponite material would be more likely to remainon vertical surfaces after application.

TABLE 3 Rheology profiles Pretreatment 7 Pretreatment 8 Pretreatment 9Shear rate (1/s) (cP) (cP) (cP) 0.01 518,000 1,180 29,300 0.1 38,100 5012,960 1 3,760 71.8 294 10 708 4.59 34.6 100 153 1.95 6.64 1000 25.9 1.413.12

Pretreatment 7 was compared against Pretreatments 8 and 9 by applyingthem to cold-rolled panels (ACT Panels) that were cleaned using Cleaner1, rinsed with deionized water. The pretreatments were applied using aplastic pipette to coat evenly with the panels in a vertical orientationat 27° C. After 5 minutes, both Pretreatment 8 and 9 started drying andthe panels exhibited flash rusting. The panels were then rinsed withdeionized water and dried by for 5 minutes at 55° C. using forced air.Pretreatment 7 did not exhibit any flash rusting.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications which are within the spirit and scopeof the invention, as defined by the appended claims.

We claim:
 1. A pretreatment composition for treating a metal substratecomprising: (a) a group IIIB metal and/or a group IVB metal present inthe pretreatment composition in an amount from 150 ppm to 1000 ppmmetal, measured on total elemental metal; and (b) a rheology modifiercomposition comprising colloidal layered silicate having an averagediameter of from 1 nm to 30 nm.
 2. The pretreatment composition of claim1 further comprising (c) a second rheology modifier composition.
 3. Thepretreatment composition of claim 1, wherein (a) the group IIIB metaland/or the group IVB metal comprises a compound of zirconium.
 4. Thepretreatment composition of claim 3, wherein the compound of zirconiumcomprises hexafluorozirconic acid, ammonium zirconium carbonate,zirconyl acetate, zirconyl nitrate, zirconyl carbonate, zirconylsulfate, zirconyl chloride, zirconium carboxylate, hydrofluorozirconicacid, zirconium acetate, zirconium oxalate, ammonium zirconiumglycolate, ammonium zirconium lactate, ammonium zirconium citrate, andmixtures thereof.
 5. The pretreatment composition of claim 1 furthercomprising: (c) an electropositive metal that is not a group IIIB metal,a group IVB metal or a group VB metal.
 6. The pretreatment compositionof claim 1, wherein (b) the rheology modifier composition is present inan amount of at least 1 percent by weight and no more than 10 percent byweight, based on the total weight of the pretreatment composition. 7.The pretreatment composition of claim 1, wherein the pH of thepretreatment composition is from 2 to
 8. 8. A method for treating ametal substrate comprising contacting the substrate with thepretreatment composition according to claim
 1. 9. A treated metalsubstrate formed according to the method of claim
 8. 10. A method fortreating a metal substrate comprising spraying an outer surface of ametal substrate with the pretreatment composition according to claim 1,wherein said sprayed pretreatment composition gels upon contact withsaid outer surface.
 11. A treated metal substrate formed according tothe method of claim
 10. 12. A method for forming a coated metalsubstrate comprising (a) contacting the metal substrate with thepretreatment composition according to claim 1 to form a treatedsubstrate; and (b) contacting the treated substrate with a coatingcomposition comprising a film-forming resin.
 13. The method of claim 12,wherein (a) contacting the metal substrate with the pretreatmentcomposition according to claim 1 to form a treated substrate comprises:spraying an outer surface of a metal substrate with the pretreatmentcomposition according to claim 1, wherein said sprayed pretreatmentcomposition gels upon contact with said outer surface.
 14. A method forforming a pretreatment composition comprising: adding a rheologymodifier composition comprising colloidal layered silicate having anaverage diameter of from 1 nm to 30 nm to an aqueous medium to form asolution; adjusting the pH of the solution to 2 and 8 with an acid toform a pH adjusted solution; and then adding a group IIIB and/or groupIVB metal to the pH adjusted solution in an amount from 150 ppm to 1000ppm metal, measured on total elemental metal.
 15. The method of claim14, wherein the rheology modifier composition comprises colloidallayered silicate.
 16. The method of claim 14, wherein the rheologymodifier composition comprises between 1 and 10 weight percent of thetotal weight of the pretreatment composition.
 17. The method of claim14, wherein the group IIIB metal and/or the group IVB metal is presentin the pretreatment composition in an amount between 150 ppm and 1,000ppm metal, measured on total elemental metal.